Oslo explosion: Is al-Qaeda behind this?

It is not yet known who – or what – was behind the gigantic explosion that hit central Oslo this afternoon. But here are three factors that are worth bearing in mind.

Possible links to al-Qaeda and terrorist networks in Britain and the US

A year ago, three men were arrested in Oslo on suspicion of preparing terrorist attacks. At the time, Norway's security service chief Janne Kristiansen said: "We believe this group has had links to people abroad who can be linked to al Qaeda, and to people who are involved in investigations in other countries, among others the United States and Britain." If this was a bomb attack, al-Qaeda will be suspected of involvement. As the BBC's Security Correspondent Frank Gardner notes, "[al-Qaeda's] AlZawahiri threatened Norway in 2007."

Suspect Shawan Sadek Saeed Bujak, an Iraqi Kurd with Norwegian residency, confessed to planning a bomb attack against Jyllands-Posten, the Danish newspaper that published the Mohammad cartoons in 2005, the police have said.

Quilliam also point out to me on Twitter: "A major Norwegian newspaper reprinted the Danish Mohammed cartoons only last year."

Norway has troops in Afghanistan

Only about 400 according to the ISAF website, but enough to attract al-Qaeda's wrath.

So far, at least one person is reported dead and dozens injured in this explosion. It happened near the Norway government's headquarters.